Harry Potter and the Half Blood Prince (film)

Plot
Lord Voldemort is tightening his grip on both the wizarding and Muggle worlds and has chosen Draco Malfoy to carry out a secret mission: to kill Albus Dumbledore. Severus Snape makes an Unbreakable Vow with Draco's mother, Narcissa, to protect Draco and fulfill the assignment if he fails.

16-year-old Harry Potter finds Dumbledore to visit former Potions professor Horace Slughorn, who has gone into hiding. Slughorn agrees to return to teach at Hogwarts. Dumbledore then takes Harry to the Burrow, where Harry is once again reunited with his best friends Ron Weasley and Hermione Granger, as well as Ron's younger sister Ginny Weasley. Harry believes Voldemort has made Draco a Death Eater, but Ron and Hermione are sceptical. On the Hogwarts Express, Harry eavesdrops on Draco using the Invisibility Cloak on the baggage shelf above him but Draco seems to have noticed Harry since he saw the baggage move a bit. Once the train arrives and everyone (including Ron and Hermione) exits, Draco uses Petrificus Totalus on Harry, takes the cloak off stomps on and breaks his nose as revenge for his father's imprisonment and throws the Cloak back on him telling him to "enjoy his ride back to London". After Draco is gone, Harry's close friend, Luna Lovegood rescues him with the Finite spell, thus breaking Draco's curse; She was able to find him due to his head being full of Wrackspurts and they walk up to the school and Harry is reunited with his friends again. Dumbledore later announces that Snape is now Defense Against the Dark Arts teacher at Hogwarts (due to Slughorn having resumed his position as Potions master) and that students were searched upon tonight because of having to make sure everything is safe now that Voldemort is at large once more.

At school, Harry and Ron have to borrow the needed textbooks for Slughorn's Potions class because they don't have their own yet. Harry's copy is inscribed on by the "Half-Blood Prince". This owner has annotated the book with additional instructions, spells and recommendations that allow Harry to excel in the class. Ron becomes Keeper of the Gryffindor Quidditch team and forms a romantic relationship with Lavender Brown, leaving Hermione disconsolate. Harry consoles Hermione, revealing that he now has feelings for Ginny.

Harry spends the Christmas holidays with the Weasleys. On Christmas Eve, Bellatrix Lestrange and Fenrir Greyback set fire to the Burrow. Back at school, Ron is nearly killed by poisoned mead, a drink originally intended for Dumbledore. While recovering, Ron murmurs Hermione's name, causing his break-up with Lavender. Harry confronts Draco and severely injures him with a Sectumsempra curse taken from the textbook of the Half-Blood Prince. Snape enters and quickly heals Draco's wounds. Fearing the book may be filled with more Dark Magic, Ginny and Harry hide it in the Room of Requirement and share their first kiss.

Dumbledore shows Harry memories of a young Tom Riddle in the orphanage he was raised in and reveals that Slughorn retains a memory critical to Voldemort's defeat. Harry succeeds in retrieving the memory, and learns that Voldemort wanted information for creating seven Horcruxes. Two of Voldemort's Horcruxes have already been destroyed: Tom Riddle's diary and Marvolo Gaunt's ring. After discovering the possible location of another Horcrux, Harry and Dumbledore travel to a seaside cave where Harry is forced to make Dumbledore drink a painful potion that hides one of the Horcruxes: a locket belonging to Salazar Slyherin. A weakened Dumbledore defends them from Inferi and they Apparate back to Hogwarts on the Astronomy Tower which they had left, where Bellatrix, Greyback and more Death Eaters have entered with Draco's help through a Vanishing Cabinet.

Dumbledore instructs Harry to hide as Draco arrives, revealing that he has been chosen by Voldemort to kill Dumbledore. Dumbledore lets Draco disarm him of the Elder Wand (Thus causing the Headmaster losing mastership of the wand to Draco) and tries to kill the Headmaster; However, he is unable to bring himself to do it, and Snape soon arrives underneath, telling Harry to be quiet, goes upstairs and he casts the Avada Kedavra curse instead, killing Dumbledore and blasting him off the Astronomy Tower as Bellatrix conjures the Dark Mark into the sky. Harry attempts to curse Snape but Snape overpowers him and reveals that he is the Half-Blood Prince. Harry returns to the school along with Hagrid to find the staff and students mourning Dumbledore as they stare at his corpse. Harry walks up to the body and strokes Dumbledore's hair, takes the locket they had recovered and puts his hand on Dumbledore's heart as Ginny sits beside Harry and comforts him as he cries. Hermione starts crying and soon McGonagall and soon Luna, Ron, Madam Pomfrey and everyone else (except Harry and Ginny) raise their wands into the sky and make the Dark Mark in the sky disappear. Harry later reveals to Ron and Hermione that the locket Horcrux was a fake. The locket contains a message from "R.A.B.", stating that he has stolen the real Horcrux with the intent of destroying it. Rather than return for their final year at Hogwarts, Harry, Ron and Hermione vow to seek out and destroy the remaining Horcruxes in order to destroy and defeat Lord Voldemort.